Manual telephone system



OFFICE Feb. 12, 1929.

J. H. LEVIS. JR

MANUAL TELEPHONE SYSTEM Filed Dec. 1, 1924 3 Sheets-83%|! 1 2 E 2 d] E;

INVENTOR JOHN H. LEVlS BY A].

ATTORNEY OPS BAR KEY Feb. 12, 1929. 1,701,575

J. H. LEVIS, JR

MANUAL TELEPHONE SYSTEM File Dec- 1924 3 Sheets-Sheet 2 To CONTACTS ONRELAY SUCH AS 26 AT ANOTHER CORD --a BUSY BACK TONE INVENTOR JOHN H.Laws, JR.

ATTO EY Patented Feb. I2, 1929.

UNITED STATES PATENT FFICE.

JOHN H. LEvIs, an, or noonnsrnn, new "roan, nssienon T0 THE momma.CARLSON TELEPHONE MAn-nrAcTnJaine COMPANY, on nociins'rnn, new YORK,-A

GORPORATION OF NEW YORK.

MANUAL TELEPHONE SYfsfEEM.

This invention relates to manual telephone systems and more particularlyto manual telephone systems of the multi-oflice type,

In former telephone systems it has usually been customary to employorder wires between an originating ofiiceandla terminating oflice forthe use of the operators in issuing instructions asto the designationofthe wantedtelephone line and for the assignment of a trunk to beemployed in completing the connection. The use or such an order wiresystem has not only resulted in numerous errors but has greatly sloweddown the eiii vention is the novel method of associating a terminatingoperators telephone set with. a trunk circuit to which a callingtelephone line has been extended. 7

Another featureof this invention is the circuit arrangement by which aset of keys, comprising one key for each source of ringing currentemployed, is common'to a group of trunk circuits and is arranged tocooperate with the circuits by which an operators telephone setisconnected to a trunk circuit taken for use.

Other features of the invention will appear in the detailed descriptionand appended claims. V

The drawings with Figs. 1 and 2 arranged in the order named and with F 8below Fig. 2, diagrammatically represent a multioliice telephone system.At the extreme left of Fig. 1 there is represented a calling subscriberssubstation and telephone line. At the left of the dotted line of thisfigure there is shown an A operators cord circuit, as well as a multipletrunk ack located at an originating office. At the right ofthis dottedline, as well as in F 2 and 3, there is represented trunk circuittogether with the c-ommon equipment associated with plurality; of

trunk circuits all located at a second office,

which is herein referred to as a terminating oilice. Atthe extreme rightof Fig. :Zthere is shown a party telephone line, only one of thesubstation circuits of which, is shown. Near theup perlelft hand cornerof Fig. 3 there is shown an operators telephone set and certainequipment which is used when manual means is used to associate theoperators telephone set with a trunk circuit. In Fig. t which isshownhelow the heavy dotted line appearing below Fig. 3, there is shownthe equipment, which is employed when autoinatic means is used toassociate an idle operators telephone set with a trunk circuit taken foruse. It will be understood that the arrangement ofFig. 4 may replacethecircuits and equipment shown in the rectangle, at'the left oi Fig. 8.The same numerals have been applied'to the corresponding conductors ofFigs. 3 and 4, so that it will be. readily understood how themodification of Fig. 4t may replace the manual cut-in arrangement withinthe rectangle, of Fig. 3. It will be noted in Fig. 3 that the conductor69 is incomplete, since it is only used with the modilication of l.

It is believed that the invention will best be understood by describingthe method of, establishing a telephone connection from, a callingsubscriber at A, whoselin'e terminates at one ollice, with asubsc-ribersline such as B, which terminates at a distant oflice. Whenthe subscriber at A initiates a call by removing his receiver fromitsswitchhook, the line relay 5, the right hand winding of which isnon-inductive, is energized in a circuit through both windings in seriesand through the back contacts of the out 01f relay 6, over both sides ofthe line in series. The operation of the line relay 5 lights the linelamp 7, whereupon, the 'A operator at the originating otfice connectsthe answering end of the cord circuit such as that shown in Fig.1 withthe jack J of the calling line. The cut-off relay 6 is then energizedover a circuit extending through'the sleeve contacts of the ad; J andthe lu P throu h 1 P e z:

the winding of the sleeve relay 8 to grounded calling line which in turnextinguishes the line lamp 7. The connection of the answering iii end ofthe cord circuit to the calling line also energizes the answeringsupervisory relay 9, which in this instance serves to supply talkingbattery to the calling line. With the relay 9 operated, the supervisorylamp 10, although its circuit is closed at the sleeve relay, still hasan open break-point in its circuit, at the armature and back contactofthe supervisory relay 9.

The operators telephone set, only the receiver of which is shown at 11,is then connected telephonically to the calling line either manually orautomatically. As shown in Fig. 1 the operators telephone set isconnected to the calling line by the depression of the listening key LK.The operator thus obtains the designation of the wanted. line and assoon as she ascertains that this line terminates at a distant oflice,she proceeds to test for an idle trunk leading to the wanted otlice.This test is accomplished bytouching the tip of the plug P to the sleeveof the jack J. Busy trunks are characterized by such a potential on thesleeve contacts of the jacks, that a dis tinctive click is heard in theoperators head set as soon as the tip or" the plug engages any ofsuchjacks. When the operator finds an idle trunk she inserts the plug Pof the cord circuit taken for use, into its jack J. This connectioneflects the energization of the relays 12 and 13 in series in a circuitextending through the sleeve contacts of ti e plug P and jack J and theenergization of the relay 13 closes a break-point in the circuit forlighting the supervisory lamp 14. When, however, the supervisory relayis energized, the lamp 14 is extinguished. The inter-engagement of thetip and ring contacts of the plug P and the jaclr J serves to complete acircuit from ground through the left hand winding of the rela 15, tipcontacts of the plug P and the jack J upper left hand winding of therepeating coil, through the high and low re sistance windings in seriesof the relay 16, lower left hand winding of the repeating coil, ringcontacts of the plug P and the jack J, right hand winding of the relay15, to grounded battery. The relay 15 does not operate in series withthe high resistance winding of the relay 16, but this last named relayattracts its arinatures and thereby effects the operation of the slowreleasing relay 17 from grounded battery, winding of this relay, upperarmature and front contact of relay 16, through the contacts 18 of theoperators individual barring key, conductor 19, to ground. With therelay 1'7 operated, relay 20 shown at the right of Fig. 2, is energizedin a circuit from grounded battery, its winding, conductor 21, outer,front contact and armature of relay 17, conductor 22, back contact andarmature of the slow releasing relay 23, to ground. Also with the relay17 operated the incoming lamp signal 24 associated with the plug Pindividual to the trunk taken for use, is intermittently lighted. Itslighting circuit extends from grounded battery, lamp 24, outer backcontact and armature of relay 25; outer armature and back contact ofrelay 26, inner right hand armature and frontcontact of relay 17,through the high resistance winding of relay 2?, to ground. The relay2'? is thus energized, but the lamp 24 does not light in series with thehigh resistance of this relay, but with the relay 2? operated the relay28 is intermittently operated in series with the interrupter 29. Eachtime that the relay 28 is energized, it extends the circuitfor the lamp24 through the low resistance left hand winding of relay 27 and thearmatures and contacts of relay 28, to ground, and since this circuit isin shunt with the high resistance winding of relay 2'7, the lamp 24 islighted.

On noting that the incoming signal lamp 24 is flashing the operatordepresses her cut-in key 30, which serves to connect her telephone setshown. in the upper left hand corner of Fig. 3, to the trunk circuit ofFig. 2. The depression of the key 30 closes a circuit from groundedbattery, winding of the slow releasing relay 31, armaturesand backcontacts of relay 32, conductor 33, left hand winding of the relay 26,conductor 34, lowermost armature and front contact of relay 20, operatedcontacts of the key 30, conductor 35, inner left hand armature andbaclr'contact of relay 25, front contact and middle arn'iature of relay17 to ground, for operating relays 26 and 31. The energization-of'relay26 extends the conductors 38 and 39 of the operators telephone set tothe trunk circuit taken for use and also closes a circuit for dimlylighting the supervisory lamp 24 to indicate to the operator to whichtrunk circuit her telephone set is connected. This lighting circuit istraceable from grounded battery, lamp 24, back contact and armature ofrelay 25, middle armature and front contact of relay 26, conductor 94,winding of the resistance coil 95, to ground. It will be noted that thiscircuit is controlled at a back contact of relay 25, so that when thislast named relay is energized at the time when ringing current isselected for the called line the lamp 24 is extinguished. The operationof the relay 31 connects the source of call-passing tone to theconductors 36, which include a windin 37 of the induction coilassociated with the operatofis telephone set. This call-passing tone istrans mitted to the A operator at the originating otlice and is a signalto that operator, that the B operator is ready to receive thedesignation of the wanted line. The tone current just referred to isinduced. in the conductors 38 and 39, which are extended through theleft hand armature and front contacts of relay 26 and thence to theright hand windings of the repeating coil, shown at the right of Fig. 1,

lUJ

over the conductors ,40 and 41. This tone current is then induced in theleft hand windings of the repeating coil and thence to head set 11. Thecall-passing tone is also heard in the B operators head set at the sametime that the A operator is notified, so that both operators on theconnection are notified to be in readiness to extend the call. lVhen therelay 26 isoperated, it is locked in this condition in aci'rcuittraceable from grounded battery, winding of the relay 32, right handarn'iature and front contact of the relay 26, winding of this relay,left hand armature and back contact of relay 25, front contact andmiddle armature of relay 17, to ground. The ener gization of there-lay32 in this last' circuit opens the original operating circuit of therelay 31, but this last named relay is now ield operated in serieswith-the resistance coil 42' and the remainder of the circuit previouslydescribed'including the conductor 33.

After receiving the call-passing tone the A operator repeats or passesthe number of the wanted telephone line to theB operator at the distantoflice. The B operator then touches the tip of the plugP of, the trunktaken for use, with the sleeve of the jack J? of the wanted line. Ifthis line is busy the B operator hears a distinctii' e click in hertelephone 67, which is a signal that the call cannot be completed.

Let be assumed that at the time of this test the wanted line is idle,whereupon the B operator inserts the plug P into the jack J of thewanted line and sinceit is also as-, sumed that the wanted line is aparty line, the operator depresses some one of the stations keys 43, 44,15 and 46 to connect the proper source of ringing current to the wantcdline to ring the desired station thereon.

With the relay 20 energized and the plug P in engagement with the jack Jthe sleeve relay 5]. is energized from grounded battery, its winding,middle front contact and armature of relay 20, sleeve contacts of theplug P and the jack J Winding of the cut-0H relay 64, to ground. Theoperation of the relay 51 causes the energization' of the relay 48 in acircuit closedfrom grounded battery. winding of this relay, inner backcontact and armature of relay 25, front contact and armature of relay51, to ground.

If the Wanted station B responds to the source of 50 cycle ringingcurrent, the operator depresses'the ringing key 4 1 which results in theenergization of the slow releasing relay 47. This last named relaythereupon attracts its armartures to complete an operating circuit forthe relay 25 of Fig. 2-, from grounded battery, left hand winding ofthis relay, uppermost front contact and armature ofrelay 4:8, conductor19, right hand front contact and armature of relay 17 to ground. Therelay 25, as soon as it is operated, closes a locking circuitfor itselffrom grounded batterythrough its right hand winding, front contact andarmature, right hand front con,- tact and armature of relay 51, toground. Also at this time the ringing frequency selecting relay 50 isenergized from groundcd battery, lowermost contact and armature of relay4:8, conductor 52, left hand front contact and armature of relay 17, toground. The relay 50 closes a locking circuit for itself throughlliSlIlllQllIlOSt front contact and armature, conductor 53, contact 51and armature of relay 55, front contact and armature of relay 51, toground; The energization of relay 47 also closes an operating circuitfrom grounded battery resistance, winding of the ringing relay 55, innerfront contact and armature of relay 48, left hand front contact andarmature ofrelay 7, to ground. The relay 55, when thus operated closes alocking circuit for itself through its front contact 5 1 and armature,right hand front contact and armature of relay 51, to ground.

Ringing current-from the 50 cycle source is now applied to thecallcdline through conductor 56, outer front contact and armature ofrelay o0, outermost back contact and armature. of relay 57,-conductor58, winding of the trip relay 59, innermost lower front contact andarmatureof relay 55, front con-' tact and armature of relay 20,through'the ring-contacts of the plug P and the ack J over the lowerside ofthe called line and through the ringer at the wanted station,over the upper side ofthe called line, tip

contacts of the jack J and the plug P upper armature and front contactof relay 20, ar mature and front contact of relay 55, to ground. Ringingcurrent is applied over this circuit until the called party answers, atwhich time the trip, relay 59 is energized to close a short'circuitaboutthe ringing relay 55, which thereupon deenergizes' and opens the ringingcircuit just traced. Also the de'energization of the ringing relay opensthe circuit of the frequency selecting relay 50, which thereuponretracts its armatures. Also when the called party answers thesupervisory relay 60 is energized over the two sides 61 and 62 of thetrunk and through the two sides of the called line in series. As

soon as this supervisory relay attracts its relay 16 extends from oneside of the high resistancewindmg of this relay, upper, front contactand armature of relay 60, outermost armature and frontcontact of relay25, conductor 63, to the other side of the high resistance winding ofrelay 16. Talking battery is supplied to the calling substation throughthe windings of the supervisory relay 9, while talking battery issupplied to the 'alled substation through the windings of thesupervisory relay 60.

it the close of the conversation, when the iarty hangs up his receiver,the supervisory retracts its arniatures to light the supervis ry lainp10. ll' hen the called party hangs up his receiver the supervisory relaydcenergizes and opens the short circuit about the hi 'h resistancewinding of the relay 16. The l gh and low resistance windings of thislast nained relay are thereupon included in the circuit previouslydescribed as extending from both windings of the supervisory relay 15,which causes this relay to retract its arniatures to li 'ht thesupervisory lamp 1&- The A operator thereupon removes the plug l? andthe plug P from the jacks with which they have been in engageinent.lVhen the relay 16 deenergises, it arises the slow releasing relay 1? toretract its arniatures and this last mention-ed relay at its outermostfront contact opens the circuitwhich has been holding the relayQOoperated. The relay :30 then retracts its arniatures and at its middlearmature and front contact opens the holding circuit of the sleeve relay51.. This last named relay at its right hand arnuturc and front contactopens the locking circuit, which has been holding the relay 25energized. Nhen the relay 20 deenergizes to open the holding circuit ofthe relay 51, it also opens the energizing circuit of the cut-off relay6d of the called line permitting it to deenergize. I

.rh-e slow releasing relay 23 is now energized from grounded batterywinding of this relay, upper back contact and armature of relay 20.through the tipcontacts of the plug P and the ack J left hand windingvof the line relay 66. to ground. The purpose of the relay 23 is toprevent 2. called subscriber such as B from being reconnected to thetrunk circuit last used, in the event that he initiates a call beforethe plug]? is removed from the jack J With this relay energized, lamp 2%is lighted as a disconnect signal in a circuit new extended fromgrounded battery lamp 2 L, back contact and armature of relay 2%.armature and back contact of the relay Q6. inner armature and backcontact of the relay 17. front contact and armature of relay 2 toground. The B operator on noting that the lltllll) 2i is'lightedsteadily, removes the plug P P'Oill the jack J WVhcn this plug isremoved from the ack, the relay 2. 3 deenergizes and all the equipmentisin readiness for usev in a succeeding call.

Let it be assumed that the wanted line was busy when the operatortouched the tip of the plug P to the sleeve ack J in testing its line.The operator then depresses one of the busy-back keys 71 to transmitbusy-back signal to the calling subscriber. will be noted that twobusy-back keys 71 have been shown, by which it was intended to indicatethat two of these keys are placed on each operators position. One ofthese keys is placed at the right of the operators position and theother key is placed at the left, so that one of these keys is easilyaccessible to either hand of the operator. When the operator depresses abusy-back key 71, a circuit is closed frolnground, contacts of this key,winding of the slow releasing relay 72, to rounded battery. Theoperation of the relay completes a circuit from ground, its ari'natureand front contact, conductor 73, outer armature and front contact ofrelay 26, inner armature and back contact of relay 51, winding of therelay 74, to grounded battery. This operates the relay '74, so that itcloses a locking circuit for itself from grounded battery, its winding,upper front contact and armature, niiddle front contact and armature ofrelay 1?, togro'und, A source of busy tone currentisconnected fromconductors 75 and 76, through the lower make contacts of relay 7% toconductors lO'and iland through the right hand windings of the repeatingcoil of f. g. 1. Busy tone current is induced in the left hand windingof therepeating Coil and thence through the condensers of the Aoperators cord circuit to the calling line. Under the control of relaysT7 and78 and interrupter 79, supervisory relay-60 is intermittentlyoperated to flash the lamp 14 as a visual indication to the A operatorthat the wanted line is busy. 7

It sometimes happens that the B operator desires to connect a trunkcircuit with another circuit without. the necessity of applying ringingcurrent tosaid circuit. Such a mentioned connection may arise when it isnecessary to extend a trunk circuit to an intercepting operator, or whenthe Boperator by mistake removes the trunk plug P from the jack J of thewanted telephone line. In such a case the subscriber is waiting on histelephone line and the connection must be reestablishedwithoutreapplying signaling current to his line. Under such conditions when theoperator desires to connecther trunk circuit to an outgoing circuitwithoutapplying ringing current, she depresses a non ring key such as 80of Fig. 3, with the result that the relay 81 is energized. Inhandling'such a call the operator depresses the non-ring key 80 at thesame stage in the operation as when she depresses a ringing key, atwhich time relays 20, 51 and 48 are operated. lVhen relay 81 attractsits armature, it closes a circuit from ground, front contact andarmature of relay 81,fconductor 49, upper armature and front contact ofrelay 48. left hand winding of relay 25, to grounded. battery. .Therelay 25 is energized and then locks itself operated in the manneralready described. The oper ation of the relay 25 extinguishes theincomof relay 26 which has been functioningto hold I the operatofistelephone et in connection with the trunk circuit. At the outer lefthand arn'iature and front contact of relay25, the short circuitincluding the conductor. ('33, about the high resistance winding ofrelay 16 of Fig. 1, is closed, so that the supervisory relay at theoriginating oflice is operated to extinguish the supervisory signal 14:.The remainder. of the connection otherwise pro ceeds in the same mannerand is released in the same way as a usual connection.

Referring now, especially to the modification of Fig. 4, it will beunderstood that this last named arrangement is provided to connect theoperators telephone set automatically to one trunk circuit at a time, towhich a calling telephine line has been extended. hen the arrangement ofFig. 4 is employed, the circuits andequipment in the rectangle at theleft of Fig. 3 are omitted and the conductors 19, 33, 38, 39, 68,69andTO are connected to correspondingly designated conductors of Fig. 4,also all cut-in keys, such as 30, are permanently held. closed. In thismodified arrangement the trunk circuits tern'iinating at an operatorsposition are arranged in groups. A suitable arrangement consists inproviding lorty trunks terminating at each operators position, dividedinto groups] of ten. It will be understood that each of these trunks maybe similar to that disclosed in Figs. 1 and 2.

When this modification is used, the initia tionof a call by thesubscriber at A is followed by the operator inserting the plug. P of anidle cord circuit into the jack J of the calling line and thendepressing a listening key LK to connect her telephone set llto thecalling telephone line. On learning that the wanted line terminates atthe distant oifice, the A operator tests the trunks in a group leadingto the wanted office by touching the tip of the plug P of her cordcircuit to the multiple trunk jacks such as J. When an idle trunk suchas that shown in Fig. l is found, the operator inserts the plug P intoits jack J. The call now proceeds in the manner already described withthe operation of the relay 16 and the consequent energization of theslow releasing relay 17 in a circuit now described from groundedbattery, its winding, upper armature and front contact of relay 16,operators bar key 18, conductor 19, to ground through contacts 82 of thekey which is used to bar the #1 group of trunks from use. The operationof the relay 1. results in the actuation of the relay 20 so that therelay Slot Fig. l is energized from grounded battery, its low resistancewinding, armature and back contact of re lay 85, contacts 86 of thegroup bar key, conductor 33, left hand winding of the relay 26,

conductor 34, lowermost armature andfront contact-of relay 20, contactsot the key now always held closed, conductor 35, inner armature and backcontact oi relay 25, middlc contact and armature o1 relay 17, to ground.As soon as the relay 8% is energized it closes a circuit from ground,its front contact and armature, left hand wlndlng of the relay 86, backcontact and armature of relay 8?, to grounded battery; Relay 86 operatesand closes a lockingv circuit for itself from grounded battery, windingof the relay 87, inner armature, front contact and right hand winding ofthe relay 86 ,frontcontacts and armatures of relay S hto ground. Theoperation of the relay 87 disables the other groups of trunks, so thatit is necessary for the operator to complete all calls existing'in onegroup of trunks, before she start-sto complete calls in any of the othergroups- Also when the relay 86 is operated, it closes an energizingcircuit for the relay 85 from grounded battery, winding of this relay,left hand front contact and armature of relay 86, conductor 68, innerarmature, front contact and winding of relay 26, inner armature and backcontact of relay 25, middle front cont-act and arn'iature of relay 17,to ground. The relay 26, when thus held operated connects the operatorstelephone set of Fig. 4 over the conductors 38 and 39 to the trunkcircuit taken for use. As soon as the relay 85is operated it opens thecircuit including only the low resistance winding of relay 84:, so thatthis last named relay is now held operated from grounded battery,through its high and low resistance windings in series and thence overconductor 33. The high resistance winding of relay 84- in this lastdescribed circuit prevents the operation of asecond relay similar to 26at another trunk circuit, in the event that calls are waiting extensionon each of two trunks atthe same time.

lVhen the B operators telephone set is connected to the trunk circuitandwhen shehas received the designation, of the wanted tele phone line, shetest-s this line by touching the tip of the plug P to the sleeve of thejack J If the wanted line is idlethe plug P is inserted into the jack Jand the operator se-, lects the proper ringing frequency by depressingsome one of the ringing keys 43700 46 inclusive. Ashas beenpreviouslypointed out this results in the operation of the relay 25,which in turn results in the deenergization of the relay 26. This lastnamed relay. on deenergization disconnects the operators telephonesetfrom the trunk, so that it can be connected to another'trunk circuit onwhich a call is awaiting extension.

The remaining operations of completing the telephone connection and for(.llSQSlitlbllShr ing the same, are identical withcorrespondingoperations previously described in connection with the arrangement wherethe op eratofls telephone set is connected to a trunk as a result of thedepression of a manual cutin key.

The foregoing description of the modified arrangement has been madewithout reference to the fact that other trunks in the same 7 group asthe one just described, as well as other trunks in other groups, maybesimultaneously awaiting the connection of the operators telephone set tothem. The circuits of Fig. l are arranged so that the operatorstelephone set is connected in succession to trunks in the same group asthe trunk to which this telephone set has just been connectcd, even iftrunks in other groups are awaiting extension by the operator. As soonas all of the trunks, awaiting extension in one group, have beenextended to the called lines, the operators telephone set is thenconnected to a trunk in the next group of runks, which group isrepresented in the lower right hand corner of f, even if trunks in thelast two groups (not shown) are awaiting extension. The means by whichthis result is accomplished will now be described.

It will be remembered that the relay of Fig. 4:, is energized throughits low resistance winding, the left hand armature and back contact ofrelay 85, contacts 86, conductor 33, left hand winding of relay 26,conductor 34;, lower armature and front con tact of relay 20,permanently closed contacts of key 30, conductor 35, inner armature andback contact of relay 25, middle contact and armature of relay 17, toground. Relays 26 and 84 are thus operated. This causes the relay 86 tobe operated in a circuit from grounded battery, left hand winding ofthis relay, front contact and armature of relay 84, to ground. Relay 86is thus operated and locks itself operated in series with the relay 8?,from grounded battery, winding of this relay, armature,front contact andwinding of relay 86, front contact and armature of relay 84, to ground.Relay 8? at its armature and back contact opens conductors such as 98,which lead to the other groups corresponding to relay 86 associated withthe other groups of trunks. \Vith the relays 86 and 26 operated, therelay is energized from grounded battery, its winding, armature andfront contact of relay 86, conductor 68, armature, front contact andwinding of relay 26, to ground through the circuit previously described.With the relay 85 thus energized, the original energizing circuit ofrelay 8%, including only the low resistance winding of this last namedrelay is opened, but. it is held operated through its high. and its lowresistance windings in series. The resistance of these two windings issuch that no other relay similar to 26, associated with trunks'of thisgroup will be operated, even though calls are awaiting extensionthereon, while the relay 26 in Fig. 2 has its operating circuit closedthrough its left hand winding. /Vhen, however, the relay 26 of Fig. 2,deenergizes, relay corresponding to 26 at another trunk circuit of thisgroup, has its operating circuit closed, so that the relay 84 is heldoperated, at. this time and continues to be held operated as long ascalls are awaiting extension in group #1. vVhen all the calls awaitingextension in a group are answered, relay 84L deenergizes, which in turncauses the relays 86 and 87 to deenergize. If a trunk in group #2 is nowawaiting extension, the relay 84 will be operated in a manner similar tothat already described, with the result'that the relays 85 and 86 areoperated. The relay 87 is also operated in series with the lockingwinding of relay 86. The operation of relay 87, at its left handarmature, disables the energizing circuit of the relay 86, associatedwith the first group of trunks, so that the operators telephone setcannot be connected with trunks of that group. At the inner-right handarma ture and back contact of relay 86, the extended starter wire 97, isopened, to disable the locking circuits of relays corresponding to 86.With the relay 86 operated, an energizing circuit for the relay 96 isclosed and this relay extends the call passing tone over the conductors36 in the manner already described.

Certain emergency equipment is provided in the present system which willnow be described. Fig. 1 there is shown a relay 90, which is connectedby conductor 70, with the operators telephone set. This relay is heldoperated as long as the operator is at her position, but when theposition is disabled, means such as a plug (not shown) functions tointerrupt the conductor 70 to effect the deenergization of relay '90,which results in the application ofv busy-tone to the trunk jack, suchas J of the trunks terminating at this operators position. This tonecircuit extends from BZ, armature and back contact of relay 90, normallyclosed contacts of the operators barring key, hack contact and armatureof relay 92, outer back contact and armature of relay 51, left handarmature and back contact of relay 17 and thence through the lower lefthand winding of the repeating coil to the jack J. Similarly when anoperator bars a trunk from use by depressing a bar key individual tothat trunk, the same tone is connected to the jack J of a circuitsimilar to that just described.

Although a plurality of battery symbols appear in the circuits of Figs.1, 2, 3 and 4, it will be understood that a single battery is employedand that this battery is connected into the circuits of the trunkofthese figures through a protecting fuse 91. If for any reason the fuseis opened the relay 92 then receives suflicient current to energize andIn the lower right hand corner of Warned against seizing trunk Whichisdisabled because of the fact that its fuse is open. a

What I claim is:

1. In a telephone system, an originating office, a terminating otfice,telephone lines terminating at each of said offices, certain 01 said.telephone lines being party lines having stations, trunks forinterconnecting said offices, means at the originating ofliceforextendinga calling telephone line terminating thereat to awtrunk, anoperators telephone set,'means controlled in part by the extension ofsaidcalling telephone line to said trunk for connecting said operatorstelephone set to saidtrunk to the exclusion of other trunks, means forextending said trunk to a Wanted telephone line, a plurality of sourcesof ringing current for signaling stations on said party lines, a singleringing key for each source of ringing current common to said trunkcircuits, and means responsive to the depression of one of said ringingkeys for selecting the proper source of signaling current to signal theWanted'station on said wanted telephone line.

2. In a telephone system, an originating oilice, a terminating ofiice,telephone lines terminating at each of said oflices, certain of saidtelephone lines being party lines l1aving stations, means at theoriginating oiiice for extending a calling telephone line termlnatingthereat to a trunk, an operators telephone set at the terminatingolfice, automatic means responsive to the extension of said callingtelephone line to said trunk for connecting said operators telephone setto said trunk to the exclusion of other trunks, means for extending saidtrunk to a Wanted telephone line, a plurality of sources of ringingcurrent for signaling stations on said party line, a single ringing keyfor each source of ringing current common to saidtrunk circuits, andmeans responsive to the depression of one of said ringing keys forsclecting the proper source ofsignaling current to signal the Wantedstation on said Wanted telephone line;

3. In a telephone system, an originating ofiice, a terminating ofiice,telephone lines terminating at each of said ofiices, certain ofsaidtelephone lines being party lines having stations, trunks forinterconnecting ,aid offices, means at the originating 'oiiice for extending a calling telephone line terminating thereat to a trunk, asignal lamp individual to said trunk, a circuit for lighting said lampwhen said trunk is extended to a calling telephone lme, an operatorstelephone set, means controlled in part by the extension of said callingtelephone line to said trunk for connecting said operators telephone setto said trunk to the exclusion of other trunks, means including aportion of said first mentioned circuituior dimly lighting said lampWhile said operators telephone setis connected to said trunk, means forextending said trunk to a Wanted telephone line, a plurality of sourcesof ringing current for signaling stations on said party lines, a singleringing key for each source of ringing current common to said trunkcircuits, and means responsive to the depression of one of said ringingkeys for. selecting the proper source of signaling currentto signal theWanted station on sai Wanted telephone line.

I. In a telephone system, an originating oliice, a terminating ofiice,telephone lines terminating at each of said ofiices, certain of saidtelephone lines being party lines having stations, trunks forinterconnecting saidoffices, means at the originating office forextending a calling telephone line terminating thereat to a trunk, asignal lampindividual to said trunk, an operators telephone 'set at saidterminating office, automatic means responsive to the extension ofsaidcalling telephone line to said trunk for connecting said operatorstelephone set to said trunk to the exclusion of other trunks, means forlighting said lamp in a distinctive manner to indicate that saidtelephone set is connected'to said trunk, means for extending said trunkto a Wanted telephone line,a plurality of sources of ringing current forsignaling stations on said party lines, a single ringing key for eachsource of ringing current common to said trunk circuits, and meansresponsive to the depression of one of said ringing keys for selectingtheproper source of signaling-current to signal the wanted station onsaid Wanted telephone line.

5. In a telephone system, an originating oil-ice, a terminating oiiice,telephone lines terminating at each of said otiices, trunks connectingsaid oilices, means at the originating oiiice for extending a callingtelephone line terminating thereat to one oi said trunks-anoperatoi"stelephone set at the terminating ()TlilCP, automatic meansresponsive to the extension of said calling telephone line tosaid trunkfor connecting said operators telephone set to said trunk to theexclusion of othertrunks and for transmitting a tone to the'originatingoffice when such connection has been made, and means for extending saidtrunk to a ,wanted telephone line.

6. In a telephone system, an originating office, a terminating olfice,telephone lines terminating at each of said oflices, certain of saidtelephonelines being party lines having stutions, trunks forinterconnecting said ofiices, means at the originating office forextendin g a calling telephone line terminating thereat to a trunk, anoperators telephone set, means p controlled in part bythe extension ofsaid ice calling telephone line to said trunk for connecting saidoperators telephone set to said trunk to the exclusion of other trunks,signaling means controlled by said operators tele phone setconnecting-means for signaling the originating oflice when saidoperators telephone set is connected to said trunk, a pluralityofsources of ringing current for signaling stationson said party lines,a single ringing key for each source of ringing current common to saidtrunk circuits, and means responsive to the depression of one of saidringing keys for selecting the proper source of signaling current tosignal the Wanted station.

7. In antelephone system, an originating ofiice, a terminating oilice,telephone lines terminating at each of said oiiices, trunks forinterconnecting said offices, means at the originating office forextending calling telephone line terminating thereat to a trunk, anoperators telephone set, means controlled in part by the extension ot'said calling telephone line to said trunkior connecting said operatorstelephone set to said trunk to the exclusion of other trunks, means forindicating when a Wanted telephone line is busy,

and means including an operator-controhcd key common to a plurality ofsaid trunks'l'or signaling the originating office that awanted line isbusy.

- 8. In a telephone system, an originating ofiice, a terminating oiiice,telephone lines terminating at each oi said oiiices, a plurality oftrunks arranged in groups for interconnect ing said oiiices, means atthe originating office for extending calling telephone lines,terminating thereat to trunks, an operators tele phone set at saidterminating oilioe, automatic means responsive to the extension of saidcalling telephone lines to said trunks for connecting said operatorstelephone set to one of said trunks to the exclusion of other trunks,said connecting means including a circuit arrangement for connectingsaid operators telephone set to other selected trunks in the same groupin succession and then for connecting said operators telephone set toother trunks of another group in succession to the temporary exclusionof all of said other groups of trunks, and means for extending selectedtrunks to wanted telephone lines.

9. In telephone system, an originating oiiice, a terminating oiiice,telephone lines terminating at each of said offices, a plurality oftrunks arranged in groups for interconnecting said oiiices, means at theoriginating oiiice for extending calling telephone lines terminatingther at to trunks, an operators telephone set at said terminatingoilice, automatic means responsive to the extension of said callingtelephone lines to said trunks for connecting said operators telephoneset to one of said trunks to the exclusion or" other trunks, saidconnecting means including a circuit arrangement forconnecting said01')- erators telephone set to other selected trunks iii-succession orthe group last used and then for, connecting said operators telephoneset to the-trunks oi? another group in succession to the temporaryexclusion of all of said other groups of trunks, signaling meansconnected to the trunk to which said operators telephone set isconnected, to indicate that said connectionhas been made, and means forextending selected trunks to Wanted telephone lines.

10. in a telephone system, an originating ofiice, a terminating office,telephone lines terminating at each of said oiiices, a plurality oftrunks arranged in groups for interconnecting said oilices, means at theoriginating oiiice extending calling telephone lines terminating thereatto trunks, an operators telephone set at said terminating oiiice,automatic means responsive "to the extension of said calling telephonelinesto said trunks for connecting said eperators telephone set to one.of said trunks to the exclusion of other trunks, said connecting meansincluding a circuit arrangement for connecting said operators telenhoneset to other selected trunks in succession of the group last used andthen for. connectingsaid operators telephone set to other trunks ofanother group in succession to the temporary exclusion of all of saidother groups of trunks, means for chaacterizing engaged telephone linesas husy,op crater controlled means for signaling the originating officethat a Wanted telephone line is busy, and means for extending selectedtrunks to idle Wanted telephone lines.

11. in a telephone system, an originating oiiice, a terminating oilice,telephone lines erininating at each of said otiices, certain of saidtelephone lines being part-y lines'with a plurality of stations, aplurality of trunks arranged in groups ioriuterconnecting said offices,means at the originating ofiice for-extending calling telephone linesterminating thereat to trunks, means for connecting trunks to Wantedtelephone lines, an operators telephone set at said terminating oiiicc,automatic means responsive to the extension of said calling telephonelines to said trunk for connecting said operatorstelephone set to one ofsaid trunks to the exclusion of other trunks, said connecting meansincluding a circuit arrangement for connecting said'operators telephoneset to other selectedtrunks in the same group in succession andthen forconnecting said operators set to other trunks of another group insuccession to'the temporary exclusion of all of said other groups oitrunks, a plurality of sources of ringing current for signaling stationson said party lines, a single key for each source of ringing current,said keys being common to said trunk circuits, and means responsive tothe depression of one of said ringing'keys for 12. In a telephonesystem, an originsting office, a terminating otlice, telephone linesterminating at each of said offices, a'plin'elity ot trunks arranged ingroups t ing said otlices, a gnal. lax each trunk, means 3.0 theoriginating ofiice for extending calling telephone li. terminatingthereat to trunks, an operators telephone set at said terminatingoffice, automatic means responsive to the extension of said callingtelephone lines said trunks for connecting said operators telephone setto one of saic. trunks to the exclusion of other trunl 's, saidconnecting means including a circuitarrangement for connecting; saidoperators telephone set to other selected trunks in the same group insuccession and then tor connecting said opera-tors telephone set toother trunks of another group in succession to the ten iporary exclusionoi all of said other groups or trunks, means for dimly lighting the lampsignal associated with the trunk to which said operators telephone setis connected, and means for extending; selected trunks to *antedtelephone lines.

l3, lln a telephone system, an orgi n ating oflice, a terminatingofiice, telephone lines terminating'at eecllot' said otlices, means atthe originating ofiicfi for extending a calling tele phonelineterminating thereat to trunk, an operators telephone set at theterminating otlice, a source of signaling current, a relay individual toeach trunk for connecting said operatofs telephone set to said trunk andfor connecting said signaling current to trunk, both of said connectionsby said relay existing concurrently, automatic means responsive to theextension of said calling telephone line to said trunlr for actuatingsaid relay, and means for extending said trunk to a wanted telephoneline.

14. In a telephone system, an originating olli-ce, a. terminatingoillce, telephone lines tel initiatingat each of said oflices, certainof said telephone lines being party lines each provided with stations,a'plurality o1: trunks arranged in groups for interconnecting saidoflices, means for connecting said trunks to wanted telephone lines, alamp individual. to each of said trunks, an. oporatofis telephone set atsaid terminating office, automatic means responsive to the extension ofsaid calling, telephone lines to said trunks for connecting saidoperators telephone set to one or said trunks of a group to theexclusion of other trunks, said connecting means including a circuitarrange 'ment for connecting said operators telephone set to otherselected trunks in the same group in succession and then for connectinq'said operators telephone set to other trunks of another group insuccession to the temporary exclusion of all of said other groups oftrunks,

' common ringing keys for selecting the proper source or signalingcurrent to signal the wanted stations on said wanted telephone lines. lI

15. In a telephone syste 'n, an originating otlice, a terminatingotlice, telephone lines tern' inating at each of said offices, trunks,each having, conductors extending between said ollices, anormally openbreak point in certain of the conductors of each trunk circuit, a relayfor closing, said break point, means in the originating otlice forextending calling telephone lines to a trunk circuit, means re SPQllSlVQto such extension for operatingsaid re ay, a second relay operated inresponse to the disconnection of said calling telephone line om saidtrunk while said trunk is connected to a calledtdephone line, saidsecond relayserving to disable said first relay, and means forconnecting said trunk to a wanted telephone line at the terminatingoffice.

16. In a telephone system, an originating otlice, a terminating office,telephone lines terminating; at eachoi said offices, trunks forinterconnecting said otfi c-es, means at the originating oliice forextending a calling telephone line terminating thereat to a trunk, anoperators telephone set, means controlled by the extensionot' saidcalling telephone line to said trunk for connecting said operatorstelephone set to said trunk tot-he exclusion of other trunks, meanstorindicating to the mg oliice that said operators telephonesetlias beenconnected to saidtrunk, means tori'ndicating when a Wanted telephoneline is busy, and means including a busy-hack key common to a pluralityof said trunlts for signalling the originating oiiice when a wanted lineis busy.

17. In a telephone system, an originating ofiice, a terminating office,telephone lines terminating at each of said ollices, certain of saidtelephone lines being provided with a plurality of stations responsiveto signalling current of different character, trunks for interconnecting said ofiices, means at the originating otlice forextending a calling telephone line terminating thereat to a trunk, anoperators telephone set, automatic means responsive to the extension ofsaid calling telephone line to said trunk for connecting said operatorstelephone set to said trunk to the exclusion of other trunks, sources ofsignalling current for signalling said stations, a single key for eachsource of current common to said trunks for selecting the proper sourceof current to signal a Wanted station on a c as ice

called telephone line, means for indicating When a Wanted telephone lineis busy, and means including a busy-back key common to a plurality ofsaid trunks for signalling the originating otfice that a Wanted line isbusy.

18. In a telephone system, an originating otlice, a terminating otiice,telephone lines terminating at each of said otlices, certain of saidtelephone lines being provided with stations, trunks for interconnectingsaid otlices, means at the originating oiiice for extending a callingtelephone line terminating thercat to a trunk, an operators telephoneset, autoniatic means responsive to the extension of said callingtelephone line to said trunk for connecting said operators telephone setto said trunk, a signal at the terminating oliice for indicating to theoperator which trunk said telephone set is connectrd, means forindicating that a wanted telephone line is busy, means including abusy-back key common to a plurality of Said trunks tor signalling theoriginating oiiice when a Wanted telephone line is busy, sources ofsignalling current for signalling said stations, and a single key foreach source oi current common to said trunks for selecting the propersource of current to signal a Wanted station on a called telephone line.

19. In a telephone system, an originating otlice, a terminating ofiice,telephone lines terminating at each of said oflices, trunks forinterconnecting said otfices, means at the originating ofiice forextending a calling telephone line terminating thereat to a trunk, anoperators telephone set, signalling means for indicating to theoriginating othce when a wanted telephone line is busy, a relayindividual to said trunk for connecting said operators telephone setthereto, said relay also serving to control in part said busy signallingmeans, and a busy-back key common to said trunks for initiating thetransmission of said busy-back signal. to the originating 20. in atelephone system, an originating oiiice, a terminating otlice, telephonelines tcrminating at each of said otiices, certain of said telephonelines being arovided with a plurality of stations responsive tosignalling current of different character, trunks for interconnectingsaid oflices, means at the orig inating otiice for extending a callingtelephone line terminating thereat to atrunk, an operators telephoneset, means responsive to the extension ot'said calling telephone line tosaid trunk for, connecting said operators telephone set to said trunk,means for transmitting a tone signal to the originating oiiice when saidoperators telephone set has been connected to said trunk, sources ofsignalling currcnt tor signalling said stations and a single key foreach source of current common to said trunks for selecting the propersource of current to signal a Wanted station on a *allcd telephone line.

In a telephone system, an originating olii-"e, a terminating oiiice,telephone lines terminating at each oi said OillCQS, a plurality oftrunks for interconnecting said otlices, means at the originating ofiicefor extending a calling telephone line terminating thereat to a trunk,an operators telephone set, means responsive to the extension of saidcalling telephone line to said trunk for connecting said operatorstelephone set to said trunk, and a tone for indicating to theoriginating oliice and to said operator that said telephone set isconnected to said trunk.

In Witness whereof, I hereunto subscribe my name this 29 day oi NovemberA. D. 1924.

JOHN H. LEVIS, J11.

